Modeling, simulating, and simplifying links between stress, attachment, and reproduction

John Bowlby's use of evolutionary theory as a cornerstone of his attachment theory was innovative in its day and remains useful. Del Giudice's target article extends Belsky et al.'s and Chisholm's efforts to integrate attachment theory with more current thinking about evolution, ecology, and neuroscience. His analysis would be strengthened by (1) using computer simulation to clarify and simulate the effects of early environmental stress, (2) incorporating information about non-stress related sources of individual differences, (3) considering the possibility of adaptive behavior without specific evolutionary adaptations, and (4) considering whether the attachment construct is critical to his analysis.

An assessment of the performance of high density polyethylene copolymers for natural gas distribution pipes

The total thermoplastics pipe market in west Europe is estimated at 900,000 metric tonnes for 1977 and is projected to grow to some 1.3 million tonnes of predominantly PVC and polyolefins pipe by 1985. By that time, polyethylene for gas distribution pipe and fittings will represent some 30% of the total polyethylene pipe market. The performance characteristics of a high density polyethylene are significantly influenced by both molecular weight and type of comonomer; the major influences being in the long-term hoop stress resistance and the environmental stress cracking resistance. Minor amounts of hexene-1 are more effective than comonomers lower in the homologous series, although there is some sacrifice of density related properties. A synergistic improvement is obtained by combining molecular weight increase with copolymerisation. The Long-term design strength of polyethylene copolymers can be determined from hoop stress measurement at elevated temperatures and by means of a separation factor of approximate value 22, extrapolation can be made to room temperature performance for a water environment. A polyethylene of black composition has a sufficiently improved performance over yellow pigmented pipe to cast doubts on the validity of internationally specifying yellow coded pipe for gas distribution service. The chemical environment (condensate formation) that can exist in natural gas distribution networks has a deleterious effect on the pipe performance the reduction amounting to at least two decades in log time. Desorption of such condensate is very slow and the influence of the more aggressive aromatic components is to lead to premature stress cracking. For natural gas distribution purposes, the design stress rating should be 39 Kg/cm2 for polyethylenes in the molecular weight range of 150 - 200,000 and 55 Kg/cm2 for higher molecular weight materials.

ERK5 is required for VEGF-mediated survival and tubular morphogenesis of primary human microvascular endothelial cells

Extracellular signal-regulated kinase 5 (ERK5) is activated in response to environmental stress and growth factors. Gene ablation of Erk5 in mice is embryonically lethal as a result of disruption of cardiovascular development and vascular integrity. We investigated vascular endothelial growth factor (VEGF)-mediated ERK5 activation in primary human dermal microvascular endothelial cells (HDMECs) undergoing proliferation on a gelatin matrix, and tubular morphogenesis within a collagen gel matrix. VEGF induced sustained ERK5 activation on both matrices. However, manipulation of ERK5 activity by siRNA-mediated gene silencing disrupted tubular morphogenesis without impacting proliferation. Overexpression of constitutively active MEK5 and ERK5 stimulated tubular morphogenesis in the absence of VEGF. Analysis of intracellular signalling revealed that ERK5 regulated AKT phosphorylation. On a collagen gel, ERK5 regulated VEGF-mediated phosphorylation of the pro-apoptotic protein BAD and increased expression of the anti-apoptotic protein BCL2, resulting in decreased caspase-3 activity and apoptosis suppression. Our findings suggest that ERK5 is required for AKT phosphorylation and cell survival and is crucial for endothelial cell differentiation in response to VEGF.